1. Field of the Invention
The present invention relates to a member position detecting apparatus used for detecting a position of a driver' seat for a vehicle, etc.
2. Description of the Related Art
An air bag apparatus provided in a vehicle enhances the safety of a driver or a passenger by inflating an air bag in response to the detection of impact in a vehicle collision. Since the air bag is inflated instantly in response to the detection of the vehicle collision, when the driver or passenger seat is adjust to the most forward position of the vehicle seat, the air bag inflating at the time of detecting the collision may severely impact the driver or the passenger.
Therefore, in order to control the operation of the air bag, there is a need for a detecting apparatus for detecting whether or not the vehicle seat of the driver or the passenger is at the most forward position at the time of the vehicle collision.
In the United States, a law requiring installation of the detecting apparatus in every newly manufactured vehicle will be in force in 2007 (US Regulation FMVSS208)
Therefore, a detecting system using a seat position sensor, for example, a magnetic sensor, was proposed (for example, see Patent Document 1).
In the system, a soft magnetic shielding plate is disposed at an outer side of a seat rail, and a magnetic sensor is disposed to extend over the soft magnetic shielding plate in order to detect the seat position according to the presence or absence of the shielding plate.
[Patent Document 1]
U.S. Pat. No. 6,053,529 (FIG. 2)
However, in the conventional art, since a shielding plate needs to be disposed outside of the seat rail and a magnetic sensor needs to be disposed to extend over the shielding plate, there are problems in that the structure is complicated and the design of layout of the seat rail is limited. Since magnetized parts are disposed outside of the seat rail, there is a problem in that dust can be easily accumulated. In addition, in a case where an external magnet of a speaker is located near the sensor, the sensor may function improperly due to the influence of the magnetic field from the external magnet.